Intravenous Fluids: Types of IV fluids

Intravenous Fluids: Types of IV fluids

William J. Kelly, MSN, FNP-C
William J. Kelly, MSN, FNP-C

Author | Nurse Practitioner

Intravenous fluids are commonly used in hospitals and emergency departments. There are many different types of IV fluids, which are used both as IV boluses as well as maintenance fluids. Understanding the difference between the types of IV fluids can be challenging, but as a nurse, it is important to understand.

Intravenous fluids featured image

Indications for Intravenous Fluids

Intravenous fluids are very commonly used in healthcare settings. Most frequently, IV fluids are used to hydrate those with dehydration. Additionally, they can be used to support blood pressure in those with hypotension or sepsis.

IV fluids can also be used as maintenance fluids for those who are not able to intake enough hydration throughout the day.

In the ER, I commonly order Intravenous fluid to those with nausea and vomiting, diarrhea, dehydration, acute kidney injury, abdominal pain, headaches, bleeding, or infections.

Maintenance Fluids vs IV Bolus

Maintenance fluids are intravenous fluids that are run at a slower rate, usually to account for decreased PO intake or expected fluid losses. Patients who are NPO (nothing by mouth) are commonly ordered maintenance fluids, as well as those with ongoing fluid losses.

Maintenance Fluids

Ongoing fluid losses commonly occur with various medical conditions. Fevers commonly require increased maintenance fluid, as they cause “insensible water losses” from sweating and overall increased metabolism.

Those experiencing frequent vomiting or diarrhea require increased fluid to account for their ongoing water losses in their vomit or stool. The same goes for those with drains experiencing significant drainage.

Those with burns or pancreatitis often require a large volume of fluids.

Those admitted with dehydration, mild hyponatremia, or acute renal failure will usually require maintenance fluids in order to slowly correct their hydration, sodium levels, and renal function.

When a patient is NPO, maintenance fluids keep the patient hydrated. To calculate maintenance fluids when a patient is NPO, you can take the patient’s body weight in Kilograms, and use the following equation: (Kg – 20) + 60 = mL/hr. (Ref).

Please note that this is not a hard rule. Those with ongoing fluid losses and various medical conditions may require a faster rate, and those who are older or with CHF may require slower rates.

Clinical Note: Just because a patient is NPO after midnight does not mean that they need maintenance fluids ordered. Do you usually drink water in the middle of the night while you sleep?

IV Bolus

IV boluses are intravenous fluids given rapidly over a short amount of time. This is most frequently used within acute care settings such as the ER or the ICU in those who are unstable with low blood pressure. Giving an IV bolus helps support blood pressure and correct hypotension.

It is common for a 1 liter IV bolus to be ordered on patients initially presenting to the ER, as fluids can help many different conditions. You will commonly see between 1-3 Liters of IV boluses, for conditions such as dehydration, sepsis, shock, migraines, abdominal pain, and n/v/d.

In sepsis, 30ml/kg boluses are commonly ordered. If a bolus is ordered, hang the bolus (usually 1L bags) by gravity and open the clamp wide open. Make sure the patient keeps their arm straight if the IV is in the AC, otherwise the bolus won’t flow.

Clinical Note: If using a pump, run the fluid at 999ml/hr. Please note that in true emergencies this may not be fast enough, and using gravity and/or a pressure bag will infuse the fluid more quickly.

Important Fluid Concepts to Understand

Before diving into the different types of IV fluids, there are a few important underlying concepts we need to understand.

Tonicity, Osmolarity, and Osmosis

Tonicity refers to a fluid’s ability to move fluid into or out of cells and is related to osmolarity – which is the total concentration of solutes within a solution. The more solutes, the higher the osmolarity.

In the body, water shifts into or out of our cell through a semi-permeable membrane – the cell wall. This means water freely flows through it, but larger solutes do not such as our electrolytes (sodium, chloride, potassium, etc).

Osmosis occurs, which is when water flows from a higher osmolarity to a lower osmolarity to “balance” out the concentrations of each side, in this case inside and outside of the cell.

Isotonic, Hypotonic, and Hypertonic Fluids

Isotonic fluids are IV fluids that have nearly the same osmolarity as intracellular fluid. This means that this IV fluid should not cause any significant net fluid shifts into or out of cells.

Hypotonic fluids are IV fluids that have a lower osmolarity than inside the cells, which causes net fluid shifts into the cells. This leads to cellular swelling, which can be deadly in certain conditions like severe head injuries and increased Intracranial Pressure (ICP).

Hypertonic fluids are IV fluids that have a higher osmolarity than inside the cells, which causes net fluid to shift out of the cells. This leads to cellular dehydration and shrinking.

Types of IV Fluids

There are many different types of IV fluids that can be ordered, and knowing the difference between them is important. Certain intravenous fluids are useful for certain situations, and others can be harmful.

As a nurse, it is important to know the basics. As a nurse practitioner, you will be responsible for ordering these fluids so this becomes even more necessary to understand.

Normal Saline (0.9% NS)

Normal Saline, NS, or NSS is the standard fluid given in both boluses and as maintenance fluids. Normal saline contains sodium chloride (NaCl) and is isotonic. This means when given through the IV, there should be no net movement of fluid or electrolyte into or out of the cells.

This ensures that there is no unnecessary swelling or shrinking of the cells when infused. Normal saline is the cornerstone intravenous fluid because it can be given for most situations, including:

  • Hydration
  • Maintenance Fluids
  • Hyponatremia
  • Hypotension or Shock
  • Sepsis
  • with Blood transfusions

Normal saline is cheap and does not result in allergic reactions, and almost all medications are compatible.

Use caution with heart failure or end-stage renal disease, and those on dialysis or in acute fluid overload should probably not receive IV fluids.

A large amount of Normal Saline (3-5+ liters) can cause significant hyperchloremic non-anion gap metabolic acidosis, especially if the patient has renal failure. This can worsen their outcomes within the hospital.

As with any IV fluid, continually monitor fluid status by making sure the patient is not having worsened lower extremity edema or new rales/crackles in the lungs.

If the patient develops sudden shortness of breath during IV fluid administration, consider fluid overload and flash pulmonary edema as a potential cause, especially with a history of heart failure.

You should always be assessing for IV infiltration as well. If there is significant swelling, blanching, and coolness near the IV site – you probably need to remove it and start a new IV.

Related articles:

Lactated Ringers (LR)

Lactated Ringers (LR) is another isotonic fluid that is commonly given. LR is the fluid of choice by surgeons, and some consider LR to be slightly better than NS, but the general consensus is that ‘One is not better than the other’.

Lactated Ringers differ from NS in that it not only has sodium chloride, but also has sodium lactate, potassium chloride, and calcium chloride.

So why choose LR over NS? LR is buffered and won’t cause the hyperchloremic metabolic acidosis that large volumes of NS can. Some studies showed improvement in renal function in critically ill patients who were on LR as opposed to NS, but the evidence is mixed.

LR can be given for all of the indications that NS can be given, including:

  • Dehydration
  • Maintenance Fluids when NPO
  • Ongoing fluid losses
  • Sepsis
  • Allergic Reactions

LR is preferred over NS in certain situations, including:

  • Pancreatitis
  • Burns
  • Surgical patients (surgeon preference)
  • Sepsis

LR should be avoided in:

  • Severe liver or renal failure
  • Metabolic alkalosis > 7.5
  • Hyperkalemia or Hypercalcemia
  • Blood transfusions (If run in the same line can cause precipitation)

As with any fluid administration, be on the lookout for fluid overload as well as local site reactions including infiltration or phlebitis.

Side Note: LR contains sodium lactate, not lactic acid. However, giving LR during sepsis can mildly influence the lactic acid level (about .9 mmol/dL), but this does not actually worsen the sepsis, and has actually giving LR has been shown to indicate lower mortality overall. Interestingly enough, NS also seems to elevate Lactic levels within in the blood. 

Intravenous Fluids IVF - Isotonic fluids

Half Normal Saline (0.45% NS)

Half normal saline (.45% NS) has half the tonicity of Normal saline. This means Half-NS is hypotonic, so the IV fluid has a lower osmolarity than the fluid inside the cells.

This means that half normal saline will cause fluid to shift inside the cells, causing the cells to swell. This can be good in certain situations, and very bad in others.

Half-Normal Saline is rarely given alone, but usually in combination with Potassium or dextrose. However, you may see slower rates given in conditions which cause significant cellular dehydration, such as with:

  • Hypernatremia
  • Severe DKA

Half-Normal saline, when run alone, is typically the wrong choice for most other scenarios as it can deplete intravascular volume and cause cellular edema. Hypotonic fluids are especially bad when it comes to:

  • Head injuries or increased ICP
  • Trauma
  • Burns
  • Liver disease

When given, make sure the patient’s sodium levels are monitored daily, as this can cause hyponatremia.

Intravenous Fluids IVF - Hypotonic fluids

Hypertonic Saline (3% NS)

Hypertonic saline is given with severe hyponatremia or with increased intracranial pressures.

Hypertonic saline is carefully and selectively given, as correcting sodium too quickly can lead to osmotic demyelination syndrome, causing irreversible neural damage.

If a patient has severe hyponatremia and symptoms consistent with cerebral edema, then hypertonic saline should be administered. These symptoms include:

  • Seizures
  • Severe headaches
  • Decreased LOC
  • Tremors

The dose is usually a 100mL bolus given over 10 minutes (a rate of 600ml/hr), which can be repeated twice if needed.

Additionally, hypertonic saline can be given in the setting of severe head injury to reduce intracranial pressure.

If your patient is ordered hypertonic saline, this needs to be on a pump, and the patient needs to be hooked up to the monitor and have frequent neuro checks. Seizure precautions should also be taken if severe hyponatremia is present.

Related article: “The Cranial Nerve Assessment for Nurses”

Hypertonic Fluids

Dextrose-Containing Solutions

Dextrose can be added to any of the fluids mentioned above, as well as to water. Dextrose solution is usually ordered for:

  • Hypoglycemia
  • Maintenance fluids

Dextrose is osmotically active, meaning it does cause the fluid to increase its tonicity, and will lead to net fluid shifts out of the cells. However, dextrose is rapidly metabolized, so the effective osmolarity tends to be higher than the base fluid, but lower than the calculated osmolarity.

Common dextrose solutions include:

  • D5W: Dextrose 5% in Water
  • D10W: Dextrose 10% in Water
  • D5NS: Dextrose 5% in NS
  • D5 1/2 NS: Dextrose 5% in 1/2 NS
  • D5LR: Dextrose 5% in LR

Overall, there is little evidence that dextrose with NS has any benefit or harm when compared to saline alone. However, dextrose should probably be added in:

  • Hypoglycemia
  • Alcohol intoxication
  • Starvation ketosis

Dextrose should not be used in:

  • Hyperglycemia
  • Hypokalemia

An amp (25gm) of 50% Dextrose (D50) is often given as an IV push medication to treat profound hypoglycemia or in conjunction with IV insulin to lower potassium levels.

D5W and D10W are often used for slow correction of chronic hypernatremia, or when hyponatremia has been too-rapidly corrected. It is often commonly found mixed with certain medications.

A patient on dextrose-solution should have their blood sugar monitored, as well as their electrolytes as with any IV fluid. Dextrose-containing solutions should not be given in boluses unless as described above with D50.

Potassium-containing Solutions

Sometimes potassium may be added to each liter bag of fluids. Potassium may be added to maintenance fluid in:

  • Hypokalemia
  • Ongoing potassium losses
  • DKA or severe hyperglycemia

Potassium is as osmotically active as sodium, so this will increase the osmolarity and cause the fluid to be more hypertonic.

This means that adding potassium to an isotonic fluid will make it hypertonic, so may not be a good choice in those with cellular dehydration like in DKA.

In these instances, adding potassium to a hypotonic base fluid such as D5NS with potassium is a great alternative option.

Remember that potassium should NEVER be used as a bolus. IV administration should not exceed 10mEq/hour in most situations, or 20mEq/hour in critical situations with cardiac monitoring and preferably a central line.

Related Article: “9 Nursing Medication Errors that KILL”

Bicarbonate-containing Solutions

Sometimes Bicarb can be added to IV fluids, in order to assist with significant metabolic acidosis. This is not super common outside of the ICU.


And that sums up IV fluids! Hopefully you found this article helpful. If you have any unanswered questions, please comment down below!

References:

Rochwerg, B. et al (2014). Fluid resuscitation in sepsis: a systematic review and network meta-analysis. Annals of internal medicine161(5), 347–355. https://pubmed.ncbi.nlm.nih.gov/25047428/

Sterns, R. H. (2020). Maintenance and replacement fluid therapy in adults. In T. W. Post (Ed.), UpToDate. https://www.uptodate.com/contents/maintenance-and-replacement-fluid-therapy-in-adults

Wilkins, L. W. (2005). Fluids and electrolytes made incredibly easy. Lippincott Williams & Wilkins.

Zitek, T., Skaggs, Z. D., Rahbar, A., Patel, J., & Khan, M. (2018). Does Intravenous Lactated Ringer’s Solution Raise Serum Lactate?. The Journal of emergency medicine55(3), 313–318. https://pubmed.ncbi.nlm.nih.gov/25047428/

Intravenous fluids Pinterest pin

Urinalysis (UA) Interpretation

Urinalysis Interpretation

Everything you need to analyze the UA

A specific cup half filled with yellow urine

William Kelly, MSN, FNP-C

Author | Nurse Practitioner

Last Updated: August 29, 2022

Urinalysis or UA is a lab test frequently ordered in all types of medical settings: hospitals (ER, ICU, Inpatient floors), urgent cares, and outpatient offices. In many cases, the correct evaluation of the urinalysis is imperative to making an accurate diagnosis. To provide additional data, many labs perform urine microscopy, giving you exact details on the contents within the urine and quantifying the results. Read all about how to interpret the Urinalysis dipstick, as well as the urine microscopy in this article!

Initial Urine Assessment

Before you even run the urinalysis, you can tell quite a bit about the patient just by using your God-given senses.

Color

The color of the urine is the easiest way to determine someone’s hydration status. Surprisingly, it can indicate other aspects of health as well.

AMBER

Normal urine varies from very clear yellow to a darker amber color. Generally speaking, the less hydrated you are – the more concentrated your urine. The more hydrated you are, the more diluted the urine, leading to clear yellow urine.

The first void of the morning is typically darker and more concentrated – this is normal. 

Red or Pink

When we see red urine – we typically think of blood. Medical conditions such as kidney stones (nephrolithiasis), UTIs, glomerular damage, or even malignancy. As little as 1mL of blood can cause a color-change, and the presence of red urine does not automatically mean large amounts of blood. There are a few different causes of red urine:

  • Bloody causes: Cystitis, kidney stones, malignancy, trauma, menstrual contamination
  • Non-bloody Conditions: Rhabdo (from myoglobin)
  • Foods: Beets, Blackberries, and Rhubarb
  • Meds: Propfolol, Chlorpromazine, Ex-Lax

Orange

Causes or orange urine include:

  • Rifampin (Antibiotic for TB)
  • Pyridium or over-the-counter AZO

Blue or Green

Also very rare, blue or green urine may be caused by:

  • Conditions: Familial benign hypercalcemia, Pseudomonas infection
  • Medications: Propofol, Amitriptyline, Indomethacin,
  • Foods: Strong Food dyes

Purple

Termed “Purple Urine Syndrome” Or “Purple Urine Bag Syndrome”, this is very rare but can occur due to:

  • Conditions: UTIs with certain gram-negative bacteria with alkaline urine
  • Meds: Amitriptyline, Methylene Blue dye
  • Foods: Diet high in Tryptophan

Turbidity

Urine turbidity is how cloudy urine is. When we see cloudy urine, our first thought should be an infection which may be accurate. However, other causes of cloudy urine are cell casts or cellular debris from kidney damage.

Smell

Stronger-smelling urine tends to mean dehydration, but foul-smelling urine usually indicates infection. This odor is caused by the bacteria that split urea to form ammonia. 

Sweet-smelling urine may mean the patient is spilling glucose into the urine from hyperglycemia.

Lastly, If the urine smells like feces, a fistula might have formed somewhere between the GI tract and the Urinary tract.

Taste?

Nah I’m just kidding – but did you know they used to taste urine to detect glucose in the urine?…. GROSS!

Urinalysis dipstick

Once you’ve assessed the urine with your own senses, it’s time to assess the actual urinalysis. This can be done in the following ways:

  1. Dipping a dipstick in urine and assessing the colors next to a test strip color chart (usually printed on the dipstick bottle).
  2. Sticking the dipstick in an Automated Urine Analyzer. This will give you. a printout of the results.
  3. Send the urine off to the lab, where they will perform a urinalysis and upload the results to your electronic medical record. They will often perform microscopy if indicated, which can be used to help interpret the urine.

Glucose

Test Levels

When serum glucose spills into the urine – this is termed glucosuria. Typically, glucose in urine does not occur until the kidney glucose threshold is reached – which is around 180mg/dL. As you can tell, this can be useful for evaluating hyperglycemia in the setting of diabetes. However, periods of stress or fever have been known to cause small amounts of glucose within the urine as well, so glucose in urine does not automatically mean diabetes

Clinical Significance

  • Glucosuria can indicate hyperglycemia in undiagnosed diabetics when blood work is not obtained.
  • Fever or stress could cause mild glucosuria in non-diabetics
  • SGLT2 inhibitors like Farxiga can increase glucose in urine even without elevated glucose levels

Testing Considerations

 

  • Ascorbic Acid (vitamin C) has been known to cause false-negatives

    Bilirubin

    Test Levels

    Urinary bilirubin may be present in low amounts in the urine normally, but increased levels are due to abnormalities of bilirubin metabolism or liver function.

    Clinical Significance

    • The presence of bilirubin may indicate elevated LFTs, but overall does not seem to add significant information toward diagnosis.

    Testing Considerations

    • Must be sent immediately as bilirubin is unstable when exposed to light

      Ketones

      Test Levels

      Normal Levels: None ( 0.3 mg/dL or  0.05 mmol/L)

      Clinical Significance

      The presence of ketones in the urine (ketonuria) indicates ketosis. This is usually caused by uncontrolled diabetes or DKA. However, acute illness, stress on the body, strenuous exercise, nausea/vomiting, and keto or other low-carb diets can cause ketonuria to occur. 

      Testing Considerations

      • Parkinson’s medications (Levodopa) can cause a false positive

        Ascorbic Acid

        Test Levels

        Normally ascorbic acid is not seen in the urine dipstick.

        Clinical Significance

        Ascorbid acid is Vitamin C. The presence of this in the urine can lead to false negatives for both Heme, glucose, leukocyte esterase, and protein.

        Testing Considerations

        Some dipsticks do add a chemical to neutralize the effect of ascorbic acid on the other tests.

        Specific Gravity

        Clinical Significance

        The specific gravity indicates how dilute or concentrated the urine is. This can give the interpreter a pretty good idea of hydration status when looking at the urinalysis.

        Test Levels

        Normal Levels: 1.005 – 1.030

        Low (<1.005): May indicate diabetes insipidus, renal failure, pyelonephritis, glomerulonephritis, psychogenic polydipsia, or malignant hypertension

        High (>1.030): May indicate severe dehydration, hepatorenal syndrome, heart failure, renal artery stenosis, shock, or SIADH.

        Testing Considerations

        • Protein, ketones, and glucose, as well as recent IV contrast dye, can falsely elevate the specific gravity.
        • Medications like diuretics can also impact this (like lasix).

        Heme

        Clinical Significance

        Heme detects blood in the urine.

        There are many potential causes of hematuria including UTIs, kidney/glomerular damage, trauma, kidney stones, malignancy, vaginal contamination, or coagulopathies.

        In a patient over 50 years old who has persistent hematuria, malignancy should be ruled out. 

          Test Levels

          Normal Levels: Negative

          The test for heme is very sensitive and can detect down to 1-2 RBCs per High-powered field (HPF). So a negative dipstick excludes blood.

          Testing Considerations

          False Negative: Unlikely, but Ascorbic acid can lead to this

          False-Positives: Myoglobin (as during rhabdomyolysis), semen (recent ejaculation), alkaline urine >9.0, contamination from hemorrhoids, vaginal blood, or oxidizing compounds used to clean the perineum can all cause false-positive heme to occur in the urinalysis.

          A positive Heme requires urine microscopy for confirmation.

           

          pH

          Clinical Significance

          The pH of urine stands for the potential of hydrogen. The more hydrogen ions there are, the more acidic something is.

          The pH scale runs of 0-14, with lower numbers being more acidic, and higher numbers being more basic.

          Because the kidneys regulate your acid/base balance, any change within the body should show up in your urine. However, various different disease processes can interfere with your kidney’s ability to do this effectively.

            Test Levels

            Normal Levels: 6, but can range from 4.6 – 8

            Acidic urine <7.0 is associated with metabolic or respiratory acidosis or an E Coli UTI.

            Basic urine >7.0 is associated with most types of kidney stones, urea-splitting bacteria (proteus or klebsiella), renal tubular acidosis, or potassium depletion.

            Testing Considerations

            Diet: Cranberries and high-protein diets can cause acidic urine, whereas citrus fruits and low-carb diets can cause alkaline urine

            Medications: Sodium bicarbonate and thiazide diuretics can cause more basic urine

            Protein

            Clinical Significance

            The urine protein dipstick is specific for albumin, which is a type of protein. Any damage to the glomerular basement membrane will let albumin and other larger particles pass through the membrane and into the urine.

            Protein in urine is typically used to evaluate kidney damage in diabetics, people with Congestive Heart Failure (CHF), or other causes of kidney damage.

            Benign causes of high protein in urine include dehydration, emotional stress, fever, heat injury, inflammation, intense activity, acute illness, or an orthostatic disorder.

            All other causes of proteinuria involve the kidney – specifically the glomerulus or the renal tubules. Some common causes of glomerular proteinuria include Diabetic nephropathy, lupus nephritis, preeclampsia, various infections (HIV, hepatitis B, post-streptococcal glomerulonephritis), certain cancers, and certain drugs like Heroin, NSAIDs, and Lithium. Some causes of tubular proteinuria include interstitial cystitis, Sickle-cell, and nephrotoxicity from NSAIDs or antibiotics like aminoglycosides.

              Test Levels

              Normal Levels: Undetectable

              The urine normally has <150mg/day of protein and should be undetectable on a dipstick, but when this level exceeds 300mg/day, high protein in urine will show up on a dipstick.

              Testing Considerations

              Urinary concentration will impact the results, so correlate with the Specific Gravity. Very dilute urine can lead to underestimation of protein, and very concentrated urine can lead to overestimation.

              In general, the dipstick is a crude estimate, and evaluation by 24-hr urine specimen is the standard of care for ongoing proteinuria. If renal cause is found, a Nephrology consult is warranted.

              In the acute setting, the dipstick for protein isn’t too informative as acute illness, inflammation, stress, and dehydration are common presentations and can cause a temporary elevation in urinary protein. 

              Urobilinogen

              Clinical Significance

              Urobilinogen is a byproduct of bilirubin production, but unlike bilirubin is colorless.

              Elevated levels can indicate malaria, hemolytic anemia, liver disease, or internal bleeding.

              An increased urobilinogen level is one of the earliest signs of liver disease and hemolytic disorders.

                Test Levels

                Normal Levels: 0.1–1 Ehrlich U/dL or 1 mg/dL

                Testing Considerations

                NA

                Nitrites

                Clinical Significance

                Nitrates are present in the urine at baseline. Some species of bacteria, specifically the Enterobacteriaceae species (E. coli, Klebsiella, Proteus, Enterobacter, Citrobacter, and Pseudomonas), release an enzyme called nitrate reductase which converts urinary nitrate to nitrite, causing nitrites in urine.

                If negative, it really doesn’t mean much. If positive, then it is highly likely an infection is present.

                  Test Levels

                  Normal Levels: Negative

                  Testing Considerations

                  This reaction requires dwelling time within the bladder to occur. Urinary frequency or the presence of a Foley catheter can make this impossible. It can take up to 4 hours of dwelling before nitrites are detected.

                  A person might not intake a sufficient amount of nitrates in their diet.

                  False-Positives: Azo dye metabolites and bilirubin, as well as letting the urine sit for too long can produce false positives. Higher specific gravity reduces the sensitivity.

                  False-Negatives: Ascorbic acid can produce false-negative.

                  Leukocyte Esterase

                  Clinical Significance

                  Leukocyte esterase is a component of WBCs that is released when these white blood cells are lysed (split open).

                  The presence of leukocyte esterase supports the diagnosis of a Urinary Tract Infection (UTI). However, the presence can also indicate various autoimmune disorders, STDs, kidney stones, or intra-abdominal infections.

                  If there is no leukocyte esterase, infection is pretty much ruled out.

                    Test Levels

                    Normal Levels: Negative

                    Testing Considerations

                    False-Negatives: Proteinuria, glycosuria, excessively concentrated urine, or tetracycline.

                    False-Positives: Contamination with vaginal discharge, certain medications (ampicillin), salicylate toxicity, and strenuous exercise.

                    Urine Microscopy

                    Urine microscopy is when they look at the patient’s urine under a microscope and further characterize the presence of certain cells. 

                    Crystals

                    Crystals, as the name implies, are crystallizations within the urine. Crystals in urine can be normal as long as they are composed of substances normally found within the urine.

                    Crystallization can occur for a variety of reasons, and the type and quantity of these will depend on the urine’s pH and underlying cause. 

                    Amorphous Crystals

                    Amorphous crystals form naturally when urine cools, and are more often found in acidic urine. This is usually just some precipitation of electrolyte salts, and there is no clinical significance.

                    Uric Acid Crystal

                    Uric acid crystals are generally associated with gout. They can also be caused by kidney stones, tumor lysis syndrome, or chemotherapy

                    Calcium Oxalate

                    Calcium Oxalate crystals are usually found in acidic urine and associated with kidney stones. Dehydration and/or increased oxalate intake can cause this. Ingestion of antifreeze can also cause these.

                    Calcium Carbonate

                    Calcium carbonate crystals may be caused by too calcium supplementation, and is also associated with kidney stones.

                    Calcium Phosphate

                    Calcium phosphate crystals are more likely to precipitate in alkaline urine. This could rarely be caused by hypoparathyroidism. 

                    Triple Phosphate

                    Triple phosphate crystals, also called Struvite crystals, are made up of magnesium ammonium phosphate. These are typically found in alkaline urine and associated with kidney stones as well as UTIs with bacteria that split urea, like Proteus mirabilis and Pseudomonas aeruginosa.

                    Hippuric Acid

                    Hippuric acid crystals are rare but can be found in normal or acidic urine.

                    Cystine

                    Cystine crystals are found in acidic urine in patients with a genetic condition called cystinuria.

                    Microrganisms

                    Bacteria are NOT normally found in the urine as it should be a sterile environment. If found, it usually indicates infection or contamination.

                    A bunch of E coli bacteria swimming around

                    Bacteria

                    Bacteria multiply rapidly if the urine specimen is left standing for too long at room temperature.

                    If there are leukocyte esterase +/- nitrites present with <15-20 epithelial cells/HPF, then infection is highly likely.

                    Consider starting empiric antibiotics if symptomatic and obtain a culture and sensitivity for confirmation.

                    Cells

                    A bunch of E coli bacteria swimming around

                    Red Blood Cells

                    Normally there are less than 2 RBCs/HPF.

                    Microscopic hematuria is defined as the presence of at least 3 RBCs/HPF.

                    Microscopic hematuria confirms a heme+ dipstick.

                    A bunch of E coli bacteria swimming around

                    White Blood Cells

                    Normally there are less than 2-5 WBCs/HPF within the urine.

                    If >5 WBCS, this indicates possible infection, inflammation, or contamination.

                    Most of the WBCs found in the case of infection are neutrophils.

                    A bunch of E coli bacteria swimming around

                    Epithelial Cells

                    Squamous epithelial cells are the skin cell of the external urethra.

                    >15-20 epithelial cells/HPF indicates contamination and another urine sample should be obtained to rule out infection.

                    Casts

                    Casts are tube-like protein structures made of various cells. Low urine pH, low urine flow rate, and high urinary salt concentration promote cast formation by favoring protein denaturation and precipitation. The presence of casts, other than hyaline casts, represents pathology within the kidney itself.

                     

                    A bunch of E coli bacteria swimming around

                    Hyaline Casts

                    Hyaline casts can be present in normal healthy adults and are nonspecific.

                    They can be found after strenuous exercise or dehydration, as well as with diuretic use.

                    A bunch of E coli bacteria swimming around

                    RBC casts

                    RBC casts usually indicate glomerulonephritis or vasculitis.

                    A bunch of E coli bacteria swimming around

                    WBC casts

                    Uncommon, but when present is usually seen with tubulointerstitial nephritis and acute pyelonephritis but also seen with renal tuberculosis and vaginal infections.

                    A bunch of E coli bacteria swimming around

                    Muddy-Brown Casts

                    Muddy-Brown Granular casts are diagnostic of acute tubular necrosis, the leading cause of Acute Kidney Injury.

                    A bunch of E coli bacteria swimming around

                    Waxy Casts

                    Waxy casts are consistent with acute or chronic renal failure.

                    A bunch of E coli bacteria swimming around

                    Broad Casts

                    Broad casts are consistenet with advanced renal failure.

                    A bunch of E coli bacteria swimming around

                    Fatty Casts

                    Fatty casts indicate nephrotic syndrome.

                    A bunch of E coli bacteria swimming around

                    Renal Tubular Epithelial Casts

                    Renal tubular epithelial cells are seen in acute tubular necrosis, interstitial nephritis, and proliferative glomerulonephritis.

                    Urinalysis UA interpretation Infographic